Antenna device and electronic apparatus including antenna device

ABSTRACT

An antenna device includes a casing including a metal casing portion and a feed coil. The metal casing portion includes a main surface, a side surface connected to the main surfaces, and a notch portion located in the side surface. The feed coil is disposed inside the casing to be coupled with the metal casing portion by a magnetic field, and includes a winding central portion forming a coil opening portion. The feed coil is disposed near the notch portion, with the coil opening portion directed to a region including the notch portion.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an antenna device including a metalcasing as an antenna and an electronic apparatus including the same.

2. Description of the Related Art

In recent years, a casing made of a metal such as aluminum or magnesiumhas sometimes been used in a mobile communication terminal such as acellular phone terminal to improve the exterior design and maintain thestrength of the casing, which is becoming larger and thinner.

If an electronic apparatus including an antenna has a metal casing,electromagnetic waves transmitted or received by the antenna are subjectto the influence of, for example, reflection and absorption by the metalcasing. When mounting the antenna in or on the electronic apparatusincluding the metal casing, therefore, the configuration, disposition,and so forth of the antenna need to be elaborated. For example, in anHF-band communication system such as NFC (Near Field Communication),simply disposing a coil antenna inside a metal casing does not enablecommunication with a communication partner.

Meanwhile, antenna devices using a metal casing as an antenna includethe one described in International Publication No. 2010/122685. Theantenna described in International Publication No. 2010/122685 includesa metal casing portion and a feed coil. A main surface of the metalcasing portion is formed with an opening portion and a slit portion. Acoil opening portion of the feed coil and the opening portion of themetal casing portion overlap, as viewed in the direction perpendicularto the main surface.

With this configuration, when a current flows through the feed coil, aninduced current flows around the metal casing portion. Further, amagnetic field passes through the opening portion and circulates tosurround the metal casing portion. Therefore, the magnetic field widelyspreads around the metal casing portion, allowing the metal casingportion to function as a part of the antenna.

In the antenna device described in International Publication No.2010/122685, it is necessary to form the opening portion and the slitportion in the main surface of the metal casing portion. However, theshape and so forth and the main surface of the electronic apparatus havesignificant influence on the design of the electronic apparatus. Theabove-described antenna device, therefore, may limit the degree ofdesign freedom of the electronic apparatus including the antenna deviceand compromise the design. Further, if the opening portion and the slitportion are formed in the main surface of the metal casing portion, thestrength of the casing is substantially reduced. According to theabove-described antenna device, therefore, a casing having sufficientstrength may not be obtained.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide an antenna devicethat provides increased strength of a casing of an electronic apparatuswithout limiting the degree of design freedom of the electronicapparatus and an electronic apparatus including the same.

An antenna device according to a preferred embodiment of the presentinvention includes a casing including a metal casing portion and a feedcoil. The metal casing portion includes a main surface, a side surfaceconnected to the main surface, and a notch portion provided in the sidesurface. The feed coil is disposed inside the casing to be coupled withthe metal casing portion by a magnetic field, and includes a windingcentral portion defining a coil opening portion. The feed coil isdisposed near the notch portion, with the coil opening portion directedto a region including the notch portion.

In this configuration, when a current flows through the feed coil, aninduced current flows through the metal casing portion coupled by themagnetic field. The induced current travels around the notch portion,and flows around the metal casing portion due to the edge effect. Then,a magnetic field is generated by the current flowing through the feedcoil and the induced current flowing through the metal casing portion.The magnetic field passes through the coil opening portion and the notchportion, and circulates to surround the metal casing portion. Therefore,the magnetic field widely spreads around the metal casing portion. It isthus possible to cause the metal casing portion to function as anantenna.

Further, in general, the shape and so forth of a main surface of anelectronic apparatus have significant influence on the design of theelectronic apparatus. In this configuration, there is no need to formthe notch portion in the main surface of the electronic apparatusincluding the antenna device. Therefore, the degree of design freedom ofthe electronic apparatus is not limited, and the design is notcompromised. Further, in this configuration, even if the notch portionis provided in the metal casing portion, the strength of the casing ofthe electronic apparatus is not significantly reduced. Accordingly, itis possible to maintain a desired or sufficient strength of the casingof the electronic apparatus.

In the antenna device according to a preferred embodiment of the presentinvention, the opening portion may extend to the main surface of themetal casing portion. In this configuration, the magnetic fieldgenerated around the metal casing portion widely spreads in thedirection in which the main surface of the metal casing portion isoriented. Even if high-frequency power supplied to the feed coil issmall, therefore, it is possible to increase the communication distanceof the antenna device not only in the direction in which the sidesurface of the metal casing portion is oriented but also in thedirection in which the main surface of the metal casing portion isoriented.

In the antenna device according to a preferred embodiment of the presentinvention, the feed coil may include a portion located near the mainsurface of the metal casing portion. In this configuration, even if thehigh-frequency power supplied to the feed coil is small, thedistribution of the induced current generated in the metal casingportion spreads to a region of the main surface of the metal casingportion distant from the notch portion. Further, the magnetic fieldgenerated around the metal casing portion widely spreads in thedirection in which the main surface of the metal casing portion isoriented. Accordingly, the direction of directivity of the antennashifts from the direction in which the side surface of the metal casingportion is oriented toward the direction in which the main surface ofthe metal casing portion is oriented, thus allowing communication usingthe main surface of the metal casing portion.

According to various preferred embodiments of the present invention, itis possible to use a metal casing portion as a part of an antenna whilemaintaining the strength of a casing of an electronic apparatus withoutlimiting the degree of design freedom of the electronic apparatus.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an external perspective view of an electronic apparatusincluding an antenna device according to a first preferred embodiment ofthe present invention, as viewed from a rear surface side thereof, andFIG. 1B is a partial side view thereof.

FIG. 2 is an external perspective view of the electronic apparatusincluding the antenna device according to the first preferred embodimentof the present invention, as viewed from an operation surface sidethereof.

FIG. 3A is a diagram illustrating a current flowing through a feed coil21, FIG. 3B is a diagram illustrating an induced current flowing througha metal casing portion 12 in a case in which the induced current islarge, and FIG. 3C is a diagram illustrating an induced current flowingthrough the metal casing portion 12 in a case in which the inducedcurrent is small.

FIG. 4 is a circuit diagram illustrating the antenna device and a feedcircuit according to the first preferred embodiment of the presentinvention.

FIG. 5A is an external perspective view of an electronic apparatusincluding an antenna device according to a second preferred embodimentof the present invention, and FIG. 5B is a partial side view thereof.

FIG. 6A is an external perspective view of an electronic apparatusincluding an antenna device according to a third preferred embodiment ofthe present invention, and FIG. 6B is a partial enlarged view thereof.

FIG. 7A is an external perspective view of an electronic apparatusincluding an antenna device according to a fourth preferred embodimentof the present invention, and FIG. 7B is a partial enlarged viewthereof.

FIG. 8A is an external perspective view of an electronic apparatusincluding an antenna device according to a fifth preferred embodiment ofthe present invention, and FIG. 8B is a partial enlarged view thereof.

FIG. 9A is an external perspective view of an electronic apparatusincluding an antenna device according to a sixth preferred embodiment,and FIG. 9B is a partial enlarged view thereof.

FIG. 10A is an external perspective view of an electronic apparatusincluding an antenna device according to a seventh preferred embodimentof the present invention, and FIGS. 10B and 10C are partial enlargedviews thereof.

FIG. 11A is an external perspective view of an electronic apparatusincluding an antenna device according to an eighth preferred embodimentof the present invention, as viewed from a front surface (operationsurface) side thereof, and FIG. 11B is an external perspective view ofthe electronic apparatus, as viewed from a rear surface side thereof.

FIG. 12 is a partial enlarged view of the electronic apparatus includingthe antenna device according to the eighth preferred embodiment of thepresent invention, as viewed from the rear surface side thereof.

FIG. 13A is an external perspective view of an electronic apparatusincluding an antenna device according to a ninth preferred embodiment ofthe present invention, as viewed from a front surface (operationsurface) side thereof, and FIG. 13B is an external perspective view ofthe electronic apparatus, as viewed from a rear surface side thereof.

FIG. 14 is a partial enlarged view of the electronic apparatus includingthe antenna device according to the ninth preferred embodiment of thepresent invention, as viewed from the rear surface side thereof.

FIG. 15A is an external perspective view of an electronic apparatusincluding an antenna device according to a tenth preferred embodiment ofthe present invention, as viewed from a front surface (operationsurface) side thereof, and FIG. 15B is an external perspective view ofthe electronic apparatus, as viewed from a rear surface side thereof.

FIG. 16 is a partial enlarged view of the electronic apparatus includingthe antenna device according to the tenth preferred embodiment of thepresent invention, as viewed from the rear surface side thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An antenna device according to a first preferred embodiment of thepresent invention will be described. FIG. 1A is an external perspectiveview of an electronic apparatus including the antenna device accordingto the first preferred embodiment, as viewed from a rear surface sidethereof, and FIG. 1B is a partial side view thereof. FIG. 2 is anexternal perspective view of the electronic apparatus, as viewed from aside thereof having a display unit and an operation unit. In thefollowing description, a surface having a large area included in outersurfaces of the electronic apparatus will be referred to as a mainsurface, and a surface substantially perpendicular to the main surfacewill be referred to as a side surface.

An antenna device 1 is a magnetic field radiation antenna that includesa casing 11 and a feed coil 21, transmits a transmission signal from thefeed coil 21 by using the casing 11 as a radiator, and/or receives areception signal from a communication partner at the feed coil 21 viathe casing 11. The casing 11 is the body itself of the electronicapparatus, and is defined by a metal casing portion 12 made of a metaland a resin casing portion 13 made of a resin. The antenna device 1 ispreferably for use in an HF-band communication system such as NFC, forexample. In NFC, the antenna device 1 is preferably used inreader/writer mode or peer-to-peer mode, for example. An electronicapparatus 2 including the antenna device 1 has an outer shape thatpreferably is a rectangular or substantially rectangular parallelepiped.The electronic apparatus 2 preferably is a mobile communication terminalsuch as a cellular phone terminal or a tablet terminal, for example.

The metal casing portion 12 preferably includes a main surface metalportion 12 a and side surface metal portions 12 b and 12 c. The metalcasing portion 12 is disposed to cover most of the casing 11 including acentral portion thereof, except for the resin casing portion 13 coveringelectric field radiation antennas (not illustrated) disposed on bothends in the long direction of the casing 11. The main surface metalportion 12 a, the side surface metal portion 12 b, and the side surfacemetal portion 12 c are disposed on a first main surface, a first sidesurface, and a second side surface of the electronic apparatus 2,respectively. The side surface metal portions 12 b and 12 c areconnected to the main surface metal portion 12 a. The resin casingportion 13 occupies the other portions of the casing 11.

An opening 31 is provided in the main surface metal portion 12 a at theposition of a camera lens. A display unit 32 and an operation unit 33 ofthe electronic apparatus 2 are disposed on a second main surface (a mainsurface opposite to the first main surface).

A notch portion 14 is provided in the side surface metal portion 12 b.The notch portion 14 is configured to communicate with a side of outeredges of the side surface metal portion 12 b perpendicular orsubstantially perpendicular to the first main surface. The notch portion14 preferably includes an opening portion 15 and a slit portion 16. Theslit portion 16 connects the opening portion 15 and the outer edge ofthe side surface metal portion 12 b. In this example, the width of theopening portion 15 is preferably the same or substantially the same asthe width of the slit portion 16.

The feed coil 21 is disposed inside the casing 11 near the side surfacemetal portion 12 b. The feed coil 21 is a spiral conductor including awinding central portion defining a coil opening portion 22. The coilopening portion 22 overlaps the opening portion 15, as viewed in thedirection perpendicular to the first side surface. The feed coil 21 iscoupled with the metal casing portion 12 by a magnetic field. Anot-illustrated circuit board is mounted inside the casing 11. A feedcircuit connected to the feed coil 21 is provided on the circuit board.

FIG. 3A is a diagram illustrating a current flowing through the feedcoil 21. FIG. 3B is a diagram illustrating a main induced currentflowing through the metal casing portion 12 in a case in which theinduced current is large. FIG. 3C is a diagram illustrating a maininduced current flowing through the metal casing portion 12 in a case inwhich the induced current is small.

If a current i1 flows through the feed coil 21, an induced current i2flows through the metal casing portion 12, which is coupled by themagnetic field, in a direction of cancelling the magnetic fieldgenerated by the current i1. If the induced current i2 is large, theinduced current i2 flows around the notch portion 14, and flows tocirculate around the metal casing portion 12 owing to the edge effect.

The magnetic field generated by the current i1 and the induced currenti2 passes through the coil opening portion 22 and the opening portion15, and circulates to surround the metal casing portion 12. Therefore,the magnetic field widely spreads around the metal casing portion 12. Itis thus possible to cause the metal casing portion 12 to function as anantenna.

If the induced current i2 is small, the induced current i2 flows aroundthe notch portion 14, and flows to circulate around a region of themetal casing portion 12 near the notch portion 14. In this case, thecommunication distance in the direction in which the first main surfaceof the electronic apparatus 2 is oriented is slightly short as comparedwith the case in which the induced current i2 is large. However, theinduced current i2 flows in the main surface metal portion 12 a also inthis case. Thus, the communication distance is increased as comparedwith a case in which the feed coil 21 alone is provided. Further, it ispossible to communicate not only with a communication partner located inthe direction in which the first side surface is oriented but also witha communication partner located in the direction in which the first mainsurface is oriented.

FIG. 4 is an equivalent circuit diagram illustrating the antenna device1 and the feed circuit. A first terminal of an RFIC 41 is connected to afirst terminal of an inductor L1. A second terminal of the RFIC 41 isconnected to a first terminal of an inductor L2. The RFIC 41 is an ICchip configured and programmed to process high-frequency signals.

A second terminal of the inductor L1 is connected to respective firstterminals of capacitors C1 and C2. A second terminal of the inductor L2is connected to a second terminal of the capacitor C1 and a firstterminal of a capacitor C3. A second terminal of the capacitor C2 isconnected to a first terminal of an inductor L3. A second terminal ofthe capacitor C3 is connected to a second terminal of the inductor L3. Avariable capacitance capacitor C4 is connected in parallel to theinductor L3. The inductor L3 corresponds to the feed coil 21. Aninductor L4 and a capacitor C5 correspond to the metal casing portion12, and are coupled with the inductor L3 by a magnetic field via theinductor L4.

The inductors L1 and L2 and the capacitor C1 define a low pass filter.The low pass filter eliminates harmonic components output from the RFIC41. The capacitors C2 and C3 define a matching circuit. The matchingcircuit matches the impedance of the RFIC 41 with the impedance of thefeed coil 21 (the inductor L3). The variable capacitance capacitor C4and the inductor L3 define a parallel resonant circuit. The resonantfrequency of the parallel resonant circuit is equal or substantiallyequal to the carrier wave frequency. The RFIC 41, the inductors L1 andL2, the capacitors C1, C2, and C3, and the variable capacitancecapacitor C4 define the feed circuit to supply power to the feed coil21. These elements are mounted on the circuit board as chip components,but may be integrated as module components, for example.

The inductance of the inductor L4 is mainly determined by the shape,size, and so forth of the opening portion 15 and the slit portion 16illustrated in FIG. 1B. The capacitance of the capacitor C5 is mainlydetermined by the shape, size, and so forth of the slit portion 16. Withthe resonant frequency of a circuit defined by the inductor L4 and thecapacitor C5 configured to be equal or substantially equal to thecarrier wave frequency, coupling with the antenna of the communicationpartner by a magnetic field is likely to occur. It is therefore possibleto provide favorable communication characteristics.

According to the first preferred embodiment, the feed coil 21 preferablyis disposed near the side surface metal portion 12 b. Further, the coilopening portion 22 overlaps the opening portion 15, as viewed in thedirection perpendicular to the first side surface. When the currentflows through the feed coil 21, therefore, the induced current in thedirection of cancelling the magnetic field flows through the metalcasing portion 12 coupled by the magnetic field. Further, the slitportion 16 connects the opening portion 15 and the outer edge of theside surface metal portion 12 b. As a result, the induced currenttravels around the opening portion 15 and the slit portion 16, and flowsaround the metal casing portion 12 due to the edge effect. Further, amagnetic field is generated by the current flowing through the feed coil21 and the induced current flowing through the metal casing portion 12.The magnetic field passes through the coil opening portion 22 and theopening portion 15, and circulates to surround the metal casing portion12. Therefore, the magnetic field widely spreads around the metal casingportion 12. Accordingly, it is possible to cause the metal casingportion 12 to function as an antenna.

Further, in general, the main surfaces of the electronic apparatus 2have significant influence on the design of the electronic apparatus 2.The notch portion 14 is preferably provided in the side surface metalportion 12 b disposed on a side surface of the electronic apparatus 2.Therefore, there is no need to change the shape and so forth of the mainsurfaces of the electronic apparatus 2. Accordingly, the degree ofdesign freedom of the electronic apparatus 2 is not limited, and thedesign is not compromised. Further, providing the notch portion 14 inthe side surface metal portion 12 b does not substantially reduce thestrength of the casing 11 of the electronic apparatus 2. It is thereforepossible to maintain the strength of the casing 11 of the electronicapparatus 2.

The notch portion 14 may be provided in both the side surface metalportions 12 b and 12 c. In this case, a first feed coil is disposed nearthe side surface metal portion 12 b, and a second feed coil is disposednear the side surface metal portion 12 c. The first and second feedcoils are connected in parallel or in series to the feed circuit. As aresult, the symmetry of the induced current flowing through the mainsurface metal portion 12 a is improved, and the directivity of theantenna is oriented in the direction perpendicular to the main surfacesof the casing 11. Communication is also possible in the direction of thetwo side surfaces.

Further, the coil opening portion 22 may not necessarily be required tooverlap the opening portion 15. If the feed coil 21 is disposed near thenotch portion 14 with the coil opening portion 22 directed to the regionformed with the notch portion 14, a magnetic field spreading around themetal casing portion 12 is generated similarly to the above description.

An antenna device according to a second preferred embodiment of thepresent invention will now be described. FIG. 5A is an externalperspective view of an electronic apparatus including the antenna deviceaccording to the second preferred embodiment, and FIG. 5B is a partialside view thereof. An antenna device 1A according to the secondpreferred embodiment includes a notch portion 14A in place of the notchportion 14 according to the first preferred embodiment. Further, theantenna device 1A according to the second preferred embodiment includesa switch unit 51A in addition to the configuration according to thefirst preferred embodiment. The switch unit 51A corresponds to anoperation unit. The other configurations preferably are similar to thoseof the first preferred embodiment. In the following, differences fromthe first preferred embodiment will be described.

The notch portion 14A preferably includes an opening portion 15A and aslit portion 16A. The width of the opening portion 15A is greater thanthe width of the slit portion 16A. The switch unit 51A is disposed inthe opening portion 15A. The switch unit 51A is, for example, a cameraswitch (shutter button), a main power switch, or a volume controlswitch. An interface unit may be disposed in the opening portion 15A.The interface unit is, for example, an IC terminal for HDMI (registeredtrademark), an earphone jack terminal, or an insertion slot for an SDcard.

According to the second preferred embodiment, it is possible to use themetal casing portion 12 as an antenna while maintaining the strength ofthe casing 11 without limiting the degree of design freedom of theelectronic apparatus 2. It is also possible to effectively use the spacein the opening portion 15A.

An antenna device according to a third preferred embodiment of thepresent invention will now be described. FIG. 6A is an externalperspective view of an electronic apparatus including the antenna deviceaccording to the third preferred embodiment, and FIG. 6B is a partialenlarged view thereof. An antenna device 1B according to the thirdpreferred embodiment includes a feed coil 21B in place of the feed coil21 according to the first preferred embodiment. The other configurationspreferably are similar to those of the first preferred embodiment. Inthe following, differences from the first preferred embodiment will bedescribed.

A portion of the feed coil 21B is disposed near the side surface metalportion 12 b. The other portion of the feed coil 21B is disposed nearthe main surface metal portion 12 a. A coil opening portion 22B overlapsthe opening portion 15, as viewed in the direction perpendicular to thefirst side surface of the electronic apparatus 2.

According to the third preferred embodiment, a portion of the feed coil21B is disposed near the main surface metal portion 12 a. Even if thehigh-frequency power supplied to the feed coil 21B is small, therefore,the induced current generated in the metal casing portion 12 spreads toa region of the main surface metal portion 12 a distant from the notchportion 14. Further, the magnetic field generated around the metalcasing portion 12 widely spreads in the direction in which the firstmain surface of the electronic apparatus 2 is oriented. Even if thehigh-frequency power is small, therefore, it is possible to increase thecommunication distance of the antenna device 1B not only in thedirection in which the first side surface of the electronic apparatus 2is oriented but also in the direction in which the first main surface ofthe electronic apparatus 2 is oriented. Further, the degree of designfreedom of the electronic apparatus 2 is not limited similarly to thefirst preferred embodiment. It is also possible to maintain the strengthof the casing 11.

An antenna device according to a fourth preferred embodiment of thepresent invention will now be described. FIG. 7A is an externalperspective view of an electronic apparatus including the antenna deviceaccording to the fourth preferred embodiment, and FIG. 7B is a partialenlarged view thereof. An antenna device 1C according to the fourthpreferred embodiment includes a feed coil 21C in place of the feed coil21 according to the first preferred embodiment. Further, the antennadevice 1C according to the fourth preferred embodiment includes a notchportion 14C in place of the notch portion 14 according to the firstpreferred embodiment. Further, the antenna device 1C according to thefourth preferred embodiment includes a switch unit 51C in addition tothe configuration according to the first preferred embodiment. Theswitch unit 51C corresponds to the operation unit. The otherconfigurations preferably are similar to those of the first preferredembodiment. In the following, differences from the first preferredembodiment will be described.

The notch portion 14C preferably includes an opening portion 15C and theslit portion 16. The opening portion 15C is preferably provided in theside surface metal portion 12 b and extends to the main surface metalportion 12 a. A portion of the feed coil 21C is disposed near the sidesurface metal portion 12 b. The other portion of the feed coil 21C isdisposed near the main surface metal portion 12 a. A portion of a coilopening portion 22C overlaps a part of the opening portion 15C, asviewed in the direction perpendicular to the first side surface of theelectronic apparatus 2. The other portion of the coil opening portion22C overlaps the other portion of the opening portion 15C, as viewed inthe direction perpendicular to the first main surface. The switch unit51C is disposed in the opening portion 15C. The switch unit 51C may bereplaced by an interface unit.

According to the fourth preferred embodiment, a portion of the feed coil21C is disposed near the main surface metal portion 12 a. Further, aportion of the opening portion 15C and a portion of the coil openingportion 22C are preferably provided in the main surface metal portion 12a. As a result, the magnetic field generated around the metal casingportion 12 widely spreads in the direction in which the first mainsurface of the electronic apparatus 2 is oriented. Even if thehigh-frequency power supplied to the feed coil 21C is small, therefore,it is possible to increase the communication distance of the antennadevice 1C not only in the direction in which the first side surface ofthe electronic apparatus 2 is oriented but also in the direction inwhich the first main surface of the electronic apparatus 2 is oriented.Further, the degree of design freedom of the electronic apparatus 2 isnot limited similarly to the first preferred embodiment. It is alsopossible to maintain the strength of the casing 11.

An antenna device according to a fifth preferred embodiment of thepresent invention will now be described. FIG. 8A is an externalperspective view of an electronic apparatus including the antenna deviceaccording to the fifth preferred embodiment, and FIG. 8B is a partialenlarged view thereof. In the following, differences from the firstpreferred embodiment will be described.

An antenna device 1D preferably is disposed on a side surface of anotebook PC 2D. The notebook PC 2D corresponds to an electronicapparatus. The electronic apparatus according to various preferredembodiments of the present invention may be a variety of electronicapparatuses such as a tablet terminal.

A casing 11D preferably includes metal casing portions 121D and 122D anda resin casing portion 13D. The metal casing portion 121D is disposed ona first main surface of the notebook PC 2D (a surface on which akeyboard 35D is disposed). The metal casing portion 122D is disposed ona second main surface thereof (a surface opposite to the first mainsurface). The metal casing portions 121D and 122D extend to sidesurfaces connecting the first and second main surfaces, and are disposedon the side surfaces via the resin casing portion 13D.

A notch portion 14D preferably includes an opening portion 15D and aslit portion 16D on the metal casing portion 121D. The opening portion15D is preferably provided in a side surface and extends to the firstmain surface. The slit portion 16D is preferably provided in the sidesurface and connects the opening portion 15D and an outer edge of themetal casing portion 121D.

A portion of the feed coil 21D is disposed near the metal casing portion121D disposed on the side surface. The other portion of the feed coil21D is disposed near the metal casing portion 121D disposed on the firstmain surface. A portion of a coil opening portion 22D overlaps a portionof the opening portion 15D, as viewed in the direction perpendicular tothe side surface. The other portion of the coil opening portion 22Doverlaps the other portion of the opening portion 15D, as viewed in thedirection perpendicular to the first main surface.

According to the fifth preferred embodiment, it is possible to use themetal casing portion 121D as an antenna while maintaining the strengthof the casing 11D without limiting the degree of design freedom of thenotebook PC 2D.

An antenna device according to a sixth preferred embodiment of thepresent invention will now be described. FIG. 9A is an externalperspective view of an electronic apparatus including the antenna deviceaccording to the sixth preferred embodiment, and FIG. 9B is a partialenlarged view thereof. An antenna device 1E according to the sixthpreferred embodiment includes a notch portion 14E in place of the notchportion 14 according to the first preferred embodiment. Further, theantenna device 1E according to the sixth preferred embodiment includes afeed coil 21E in place of the feed coil 21 according to the firstpreferred embodiment. The other configurations preferably are similar tothose of the first preferred embodiment. In the following, differencesfrom the first preferred embodiment will be described.

The notch portion 14E preferably includes an opening portion 15E and aslit portion 16E. The opening portion 15E is preferably provided in theside surface metal portion 12 b, and is in contact with the boundarybetween the main surface metal portion 12 a and the side surface metalportion 12 b. The slit portion 16E connects the opening portion 15E andan outer edge of the side surface metal portion 12 b. The outer edge isa side of the outer edges of the side surface metal portion 12 bparallel to the first main surface of the electronic apparatus 2.

A portion of the feed coil 21E is disposed near the side surface metalportion 12 b. The other portion of the feed coil 21E is disposed nearthe main surface metal portion 12 a. A coil opening portion 22E overlapsthe opening portion 15E, as viewed in the direction perpendicular to thefirst side surface.

According to the sixth preferred embodiment, it is possible to use themetal casing portion 12 as an antenna while maintaining the strength ofthe casing 11 without limiting the degree of design freedom of theelectronic apparatus 2.

An antenna device according to a seventh preferred embodiment of thepresent invention will now be described. FIG. 10A is an externalperspective view of an electronic apparatus including the antenna deviceaccording to the seventh preferred embodiment, and FIG. 10B is a partialenlarged view thereof. An antenna device 1F according to the seventhpreferred embodiment includes a feed coil 21F in place of the feed coil21 according to the first preferred embodiment. The other configurationspreferably are similar to those of the first preferred embodiment. Inthe following, differences from the first preferred embodiment will bedescribed.

The feed coil 21F preferably includes a chip coil including a coilconductor arranged around a magnetic material. A coil opening portion22F overlaps the opening portion 15, as viewed in the directionperpendicular to the first side surface. The feed coil 21F is mounted onthe not-illustrated circuit board together with the feed circuit.

Further, the feed coil defined by a chip coil may be disposed as in FIG.10C. An antenna device 1G includes a feed coil 21G defined by a chipcoil. An opening surface of a coil opening portion 22G is disposed to beperpendicular or substantially perpendicular to a main surface of theside surface metal portion 12 b. The feed coil 21G is disposed near thenotch portion 14 with the coil opening portion 22G directed to theregion formed with the notch portion 14. As a result, a magnetic fieldis generated to pass through the coil opening portion 22G and theopening portion 15. Therefore, the feed coil 21G is coupled with themetal casing portion 12 by the magnetic field.

According to the seventh preferred embodiment, it is possible to use themetal casing portion 12 as an antenna while maintaining the strength ofthe casing 11 without limiting the degree of design freedom of theelectronic apparatus 2.

An antenna device according to an eighth preferred embodiment of thepresent invention will now be described. FIG. 11A is an externalperspective view of an electronic apparatus including the antenna deviceaccording to the eighth preferred embodiment, as viewed from a frontsurface (operation surface) side thereof, and FIG. 11B is an externalperspective view of the electronic apparatus, as viewed from a rearsurface side thereof. FIG. 12 is a partial enlarged view of theelectronic apparatus, as viewed from the rear surface side thereof. Inthe following, differences from the first preferred embodiment will bedescribed.

An antenna device 1H includes a metal casing portion (upper casing)121H, a metal casing portion (lower casing) 122H, and a feed coil 21H.The metal casing portion 121H preferably includes a front surface metalportion 121 aH and a side surface metal portion 121 bH.

The front surface metal portion 121 aH preferably has a flat orsubstantially flat plate shape, and defines a front surface of a casing11H of an electronic apparatus 2H. The front surface metal portion 121aH preferably includes opening portions, in which the display unit 32and the operation unit 33 are disposed. The side surface metal portion121 bH preferably has a frame shape, and is disposed to cover most ofside surfaces of the casing 11H. The front surface metal portion 121 aHand the side surface metal portion 121 bH are connected to define thebox-shaped metal casing portion 121H. The metal casing portion 122Hpreferably has a flat plate shape, and forms a rear surface of thecasing 11H. A gap between the metal casing portion 121H and the metalcasing portion 122H is occupied by a frame-shaped resin casing portion(gap portion) 13H.

The feed coil 21H is disposed inside the casing 11H along the sidesurface metal portion 121 bH and the metal casing portion 122H. A coilopening portion 22H of the feed coil 21H overlaps the resin casingportion 13H, as viewed in the direction perpendicular to a side surfaceof the casing 11H having the feed coil 21H disposed thereon. The outerdimension of the feed coil 21H is long in the long direction of thecasing 11H and short in the short direction of the casing 11H.

The metal casing portion 121H and the metal casing portion 122H may beconnected at predetermined locations. If the metal casing portion 121Hand the metal casing portion 122H are connected with connectionconductors, however, providing two connection conductors near both sidesof the feed coil 21H is avoided. This is because shortcut of the inducedcurrent may occur in the metal casing portions 121H and 122H, and theinduced current may flow only in portions of the metal casing portions121H and 122H near the feed coil 21H.

According to the eighth preferred embodiment, the resin casing portion13H is disposed offset to be closer to the rear surface of the casing11H, and the feed coil 21H is disposed along a side surface and the rearsurface of the casing 11H. Therefore, the antenna device 1H hasdirectivity in the direction of the rear surface of the electronicapparatus 2H.

Further, as described above, the outer dimension of the feed coil 21H islong in the long direction of the casing 11H and short in the shortdirection of the casing 11H. That is, the feed coil 21H is configuredand disposed such that the overlapping area of the coil opening portion22H of the feed coil 21H and the resin casing portion 13H is increasedas much as possible. As a result, the coupling of the metal casingportions 121H and 122H and the feed coil 21H by the magnetic field isreinforced. Accordingly, the radiation efficiency of the antenna device1H is increased.

According to the configuration of the eighth preferred embodiment, it ispossible to use the metal casing portions 121H and 122H as an antennawhile maintaining the strength of the casing 11H without limiting thedegree of design freedom of the electronic apparatus 2H.

An antenna device according to a ninth preferred embodiment of thepresent invention will now be described. FIG. 13A is an externalperspective view of an electronic apparatus including the antenna deviceaccording to the ninth preferred embodiment, as viewed from a frontsurface (operation surface) side thereof, and FIG. 13B is an externalperspective view of the electronic apparatus, as viewed from a rearsurface side thereof. FIG. 14 is a partial enlarged view of theelectronic apparatus, as viewed from the rear surface side thereof. Inthe following, differences from the first preferred embodiment will bedescribed.

An antenna device 1J includes a metal casing portion (frame-shapedcasing) 121J, a metal casing portion (lower casing) 122J, and a feedcoil 21J. The metal casing portion 121J preferably has a frame orsubstantially frame shape, and is disposed to cover most of sidesurfaces of a casing 11J of an electronic apparatus 2J. A slit portion(gap portion) 16J made of a resin is configured to connect one endsurface and the other end surface of the metal casing portion 121J. Theslit portion (gap portion) 16J extends in the thickness direction(vertical direction) of the casing 11J. The metal casing portion 122Jpreferably has a flat plate shape, and defines a rear surface of thecasing 11J. A gap between the metal casing portion 121J and the metalcasing portion 122J is occupied by a frame-shaped resin casing portion(gap portion) 13 bJ. The other portion of the casing 11J including thefront surface thereof is occupied by a resin casing portion (uppercasing) 13 aJ. The slit portion 16J may be provided in another portionof the metal casing portion 121J. That is, the slit portion 16J may beprovided not in a portion of the metal casing portion 121J correspondingto the long direction of the casing 11J but in a portion of the metalcasing portion 121J corresponding to the short direction of the casing11J.

The feed coil 21J is disposed inside the casing 11J along the metalcasing portion 121J and the metal casing portion 122J. A coil openingportion 22J of the feed coil 21J overlaps a portion in which the slitportion (gap portion) 16J and the resin casing portion (gap portion) 13bJ are connected, as viewed in the direction perpendicular to a sidesurface of the casing 11J including the feed coil 21J disposed thereon.The outer dimension of the feed coil 21J is long in the long directionof the casing 11J and short in the short direction of the casing 11J.

The metal casing portion 121J and the metal casing portion 122J may beconnected at predetermined locations. If the metal casing portion 121Jand the metal casing portion 122J are connected with connectionconductors, two connection conductors are preferably provided near bothsides of the feed coil 21J. Further, the resin casing portion (gapportion) 13 bJ, which is disposed around the entire circumference of thecasing 11J, is not necessary required to be provided around the entirecircumference. For example, the slit portion (gap portion) 16J and theresin casing portion (gap portion) 13 bJ may define a T-shaped slit.

According to the ninth preferred embodiment, the slit portion 16J isprovided in the metal casing portion 121J. Similarly to the firstpreferred embodiment, therefore, an induced current flows around themetal casing portion 121J, 122J, and a magnetic field widely spreadsaround the metal casing portions 121J and 122J. As a result, theradiation efficiency of the antenna device 1J is increased, and it ispossible to increase the communication distance of the antenna device1J.

Further, effects similar to those of the eighth preferred embodiment arealso obtainable by the ninth preferred embodiment.

An antenna device according to a tenth preferred embodiment of thepresent invention will now be described. FIG. 15A is an externalperspective view of an electronic apparatus including the antenna deviceaccording to the tenth preferred embodiment, as viewed from a frontsurface (operation surface) side thereof, and FIG. 15B is an externalperspective view of the electronic apparatus, as viewed from a rearsurface side thereof. FIG. 16 is a partial enlarged view of theelectronic apparatus, as viewed from the rear surface side thereof. Inthe following, differences from the first preferred embodiment will bedescribed.

An antenna device 1K includes a metal casing portion (upper casing)121K, a metal casing portion (lower casing) 122K, and a feed coil 21K.The metal casing portion 121K includes a front surface metal portion 121aK and a side surface metal portion 121 bK. The metal casing portion122K includes a rear surface metal portion 122 aK and a side surfacemetal portion 122 bK.

The front surface metal portion 121 aK preferably has a flat orsubstantially flat plate shape, and defines a front surface of a casing11K of an electronic apparatus 2K. The front surface metal portion 121aK preferably includes opening portions, in which the display unit 32and the operation unit 33 are disposed. The side surface metal portion121 bK has a frame shape, and is disposed on side surfaces of the casing11K to be closer to the front surface. The front surface metal portion121 aK and the side surface metal portion 121 bK are connected to definethe box-shaped metal casing portion 121K.

The rear surface metal portion 122 aK preferably has a flat orsubstantially flat plate shape, and defines a rear surface of the casing11K. The rear surface metal portion 121 aK is provided with an opening31 at the position of a camera lens. The side surface metal portion 122bK has a frame shape, and is disposed on the side surfaces of the casing11K to be closer to the rear surface. The rear surface metal portion 122aK and the side surface metal portion 122 bK are connected to define thebox-shaped metal casing portion 122K.

A gap between the metal casing portion 121K and the metal casing portion122K is occupied by a frame-shaped or substantially frame-shaped resincasing portion (gap portion) 13K. The resin casing portion 13K isdisposed to be closer to the rear surface. The resin casing portion 13Kpreferably includes an opening portion, in which a switch unit 51K isdisposed. As described above, the switch unit 51K is, for example, aterminal main power ON/OFF switch, a volume control switch, or a shutterbutton of a camera.

The feed coil 21K is disposed inside the casing 11K along the sidesurface metal portion 121 bK and the metal casing portion 122K. A coilopening portion 22K of the feed coil 21K overlaps the resin casingportion 13K, as viewed in the direction perpendicular to a side surfaceof the casing 11K having the feed coil 21K disposed thereon. The outerdimension of the feed coil 21K is long in the long direction of thecasing 11K and short in the short direction of the casing 11K. The resincasing portion 13K is disposed offset to be closer to the rear surfaceof the casing 11K, and the feed coil 21K is disposed along the sidesurface and the rear surface of the casing 11K.

The metal casing portion 121K and the metal casing portion 122Kpreferably are connected at predetermined locations. If the metal casingportion 121K and the metal casing portion 122K are connected withconnection conductors, however, providing two connection conductors nearboth sides of the feed coil 21K is avoided.

According to the tenth preferred embodiment, it is possible to obtaineffects similar to those of the eighth preferred embodiment.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. An electronic apparatus comprising: a casingincluding a first metal casing portion and a second metal casingportion; and a feed coil disposed inside the casing, and including awinding central portion defining a coil opening portion; wherein thefirst metal casing portion and the second metal casing portion are notcontinuous with each other and are separated by a slit located on afirst surface of the casing; and when the first surface is viewed inplan view, the feed coil overlaps both of the first metal casing portionand the second metal casing portion.
 2. The electronic apparatusaccording to claim 1, wherein the first metal casing portion and thesecond metal casing portion are not galvanically connected.
 3. Theelectronic apparatus according to claim 1, wherein the feed coil has alonger side direction and a shorter side direction; and the longer sidedirection is substantially parallel to a direction in which the slitextends.
 4. The electronic apparatus according to claim 1, wherein theslit is filled with a plastic casing portion.